Google Sheet - Redirect Script

I have a working Google Sheet which requires minor changes. When a URL is entered into column A, the end result is shown in column B. This helps show where a shortened URL is going. We have some minor changes required. 1.) Only 1 column. When the URL is added or edited in column A, we will update that cell with the result. No need for both columns. 2.) Resource Heavy We will only need to refresh cells which have been edited. I believe part 1 above will resolve this. You must be experienced at JS. Thanks